The present invention relates in general to a radio selective calling system for adding a transmission number to data to carry out the data transmission when the data is transmitted from a transmission system site to each of radio selective calling receivers, and more particularly, in this system, to a radio selective calling receiver which is provided with a facility for detecting retransmission data and an omission of the data on the basis of the transmission number contained in the received data.
In a radio selective calling system of this sort, when the data is transmitted from the transmission system site to each of the radio selective calling receiver, the assignment of the transmission number is carried out for every radio selective calling receiver, and the data is transmitted with the transmission number added to the associated data. In addition, there is the case where the data identical to the data which has already been transmitted is transmitted again from the transmission system. In such a case, however, the transmission number identical to the transmission number which was added to the data once is added to the data, and then the data is retransmitted. Incidentally, as for the system for carrying out the control in such a way that such a transmission number is added to the associated data and the data having the transmission number added thereto is transmitted, there is, for example, a well known system is designed in accordance with FLEX as the world-wide general standard, or ERMES as a European Standard.
On the other hand, in the radio selective calling receiver for use in the radio selective calling system of this sort, since the signal is received with the new data and the retransmission data mixed with each other as described above, the control for the reception based on the transmission number is carried out as follows:
(1) When the signal has been received, the transmission number is detected from the signal thus received. PA1 (2) The received data which was received is stored in the order of the transmission numbers in the storage means. PA1 (3) The transmission number which has been newly received and the data which has been received so as to follow the transmission number are compared with the newest M (M is an integral number) transmission numbers, which are stored in the above-mentioned storage means, and the newest M data received so as to follow the newest M transmission numbers, respectively. As a result, when the transmission number and the received data following the transmission number which are respectively identical in contents to those which have been received this time are present in the newest M transmission numbers and the newest M received data, respectively, the data which has been received this time is regarded as the retransmission data, and hence the warning for the data reception is not carried out. PA1 (4) When the difference between the transmission number which has been newly received and the newest transmission number stored in the above-mentioned storage means is detected and it is equal to or larger than two, the warning that the data is failed to be received through the transmission data is present (hereinafter, referred to as "a data omission" for short, when applicable) is output. That is, when any transmission number is skipped, it is judged that there is a data omission, and then the user is informed of this fact. PA1 153, 152, 151, 150 PA1 148, 153, 152, 151 PA1 detection means for detecting both transmission data and its transmission number from a received signal; PA1 storage means for successively storing therein said detected data and their transmission numbers; PA1 retransmission data judging means for judging, when a newly received transmission number is older than a newest transmission number stored in said storage means and also a difference between said newly received transmission number and said newest transmission number is equal to or smaller than X (X is an arbitrary setting value), that said newly received data is retransmission data; PA1 data omission judging means for judging, when a newly received transmission number is older than the newest transmission number stored in the storage means and also the difference between said newly received transmission number and said newest transmission number is larger than said X, that a data omission is present in said data in reception; and PA1 control means for writing, when judgment that said newly received data is said retransmission data was not carried out by said retransmission data judging means, both said newly received data and its transmission number to said storage means and also carrying out warning for said data reception, and warning for said data omission, when judgment that there was a data omission was carried out by said data omission judgment means.
An example of above-mentioned invention, JP-A-267825/1991 disclosed a radio selective calling receiver.
Now, in the above-mentioned conventional radio selective calling receiver, there arises the problem that when the retransmission data is received which has the transmission number older than any one of the newest M transmission numbers stored in the storage means, each of the above-mentioned warnings is not properly issued. This problem will hereinbelow be described by taking a concrete example.
For example, it is assumed that the newest M (M=4 in this example) transmission numbers out of the transmission numbers which have been received until now are stored in the storage means as follows:
Then, it is assumed that under this condition, the retransmission data having the transmission number "148" is received. In this case, since the transmission number "148" is absent in the newest M transmission numbers, the data thus received is treated as the wholly new received data though it is the retransmission data, and hence the warning that the transmission data has been newly received is issued.
In addition, as a result of writing the transmission number "148" of the received data to the storage means since the received data is judged to be the wholly new received data, the newest M transmission numbers stored in the storage means are as follows.
Then, it is assumed that thereafter, the data having the transmission number "154" is received. In this case, since the transmission number of the newest received data is "148", in the conventional radio selective calling receiver, it is judged that the data omission occurs in the reception of the data of the transmission numbers ranging from "147" to "154".
Thus, in the conventional radio selective calling receiver, when the retransmission data having the transmission number which does not match any one of the newest M transmission numbers stored in the storage means, it is not detected that the data of interest is the retransmission data, and also the retransmission data is treated as the new transmission data. As a result, when the new transmission data is then received, the mistaken warning for the data omission in reception is issued.